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THE LANDING: BLOG

Cruising the code zero.

Chuck Skewes of Ullman Sails San Diego

By Chuck Skewes of Ullman Sails San Diego

Many sailors, especially cruisers, shy away from cruising the code zero, despite the sail’s versatility and ability to add significant increases in boat speed. In this article we remove some of the mystique around this specialty sail and explain how it can be used to enhance anyone’s sailing experience.

What exactly is a code zero?  

Officially a code zero is a spinnaker for use in tight-reaching in light air – that’s it!  The sail tends to be the smallest spinnaker in any sail inventory, whether racing or cruising.  Racers have discovered that because of its size and applicable wind strength and angle ranges, the sail has benefits for racing performance while avoiding rating penalties. However, the practical applications of the sail apply just as much (if not more) to cruising boats.

The code zero was introduced in the 1997/98 Whitbread (now Volvo) Round the World Race.  The event winners, Paul Cayard and the crew of ‘EF Language’, used a very small, tight-reaching spinnaker that could be used while the other teams could only use their genoas.  It was very successful and since its introduction racers around the world have followed suit.  The sail is considered a spinnaker instead of a genoa because of its dimensions.  Sails built with a mid-girth length (the shortest distance between the leech mid-point and the luff) greater than or equal to 75% of the foot length qualify as spinnakers. The code zero meets this requirement. The mid-girth measurement is used in the rules to prevent teams from making 180% genoas and calling them spinnakers without the sail impacting their rating.

How does the sail cross-over for cruising?

Since cruising sails don’t have to meet any racing requirements we can actually make a much better sail for cruisers.  The sail works like a very light, very large genoa.  With a cruising code zero we can make the leech much straighter vertically, which allows us to make a straighter exit for the wind.  This reduces heel and makes the sail more efficient and versatile. Essentially it provides more horsepower in light air, making sailing much more enjoyable. It is ideal for modern boats that have small non-overlapping headsails.

If someone occasionally races in beer-can races, can they use the cruising code zero to race?

A cruising code zero will rate as a genoa, so if it is larger than your largest genoa (and they always are!) you have to report it or not use it.

What wind ranges and wind angles do you use a cruising code zero in?

You can typically use a cruising code zero from 70° true wind angle (TWA) in very light air up to 110° TWA in 15+knts.  Ultimately it depends on the righting moment of your boat and how comfortable you are with how much the sail may make your boat heel in significant breeze or at tighter angles.  Most cruising code zeros are designed primarily for use in 85°-100°TWA.

How much extra performance should I expect to get out of a cruising code zero?

In light air the added speed generated from the sail is significant.  It often more than doubles your sail area and can increase performance up to 30% as compared to a non-overlapping genoa.

If a code zero is for light wind, does that mean I’ll be motoring less? Do you use it for offshore cruising? Or would I use it in a harbor as well?

We use the code zero anytime the wind angle and wind strength are correct, whether we are in the harbor or on a long cruise.  The light air performance will allow you to sail more and motor less, which, at least among our customers, we’ve found is typically the goal.

Are code zeros furling sails?  Are they easy to launch?  How many people do you need to do that? 

Ullman Sails can design a code zero either as a furling sail or to launch from a sail bag.  I recommend furling because you can set it up at the dock and easily roll and unroll the sail as the wind velocity and your angle change.  Also, if you furl the sail, it can be used while single-handing. If you bag launch the sail you will want 3 or more crew on deck.

Have you had experience cruising with a code zero?  Do you have a question we didn’t answer? What impact did it have on your sailing experience? Any advice you can offer to other sailors considering adding the sail to their inventory?

About Chuck Skewes A Seattle, Washington native, Chuck is an avid pro sailor and sailmaker.  In just the last year Chuck has been part of the winning crews in the International Masters, Beneteau 36.7 West Coast Championships, and the Tjorn Runt in Sweden.  He is also the loft manager at Ullman Sails San Diego and Ullman Sails Pacific Northwest. Chuck currently resides in San Diego and has been sailmaking since 1984.

Home > Education & Expertise > Downwind and Light Wind Sails > Code Zero

Code Zero Sail

The Code Zero is a spinnaker-genoa hybrid. It’s designed to operate like a genoa but considered a spinnaker under racing rules (depending on its dimensions). This cruiser’s dream sail helps a boat’s performance in close reaching angles, especially in lighter winds, by generating much more speed than a slightly eased head sail. These sails also reach very well in moderate wind. A low stretch Vectran/Dyneema line or a torsion cable is normally used for the luff, and the sail is tensioned firmly to get a straight luff (a lot like a genoa).

A Code Zero has a mid girth of 75% of the foot length, so it measures as a spinnaker but has a much bigger area than a genoa. The optimal wind speed for this sail is 3 to 18 knots true wind speed and in lighter winds, you can carry this sail up to a 45-degree true wind angle. Typically they are designed to be flatter than a spinnaker and have a straight leech exit.

High-quality Code Zeros that’ll stand the test of time, no matter what you’re up to.

What makes a code zero.

The Code-Zero should be recognized as a spinnaker in the racing community, which means it must have a Mid Girth (MGM) no less than 75% of the Spinnaker Foot Length (SF).

The Code-Zero should  have a solid luff, unlike drifters or Asymmetric Spinnakers which are free-run, attached only at the head, tack, and clew.  The Code-Zero is run off of a dyneema or torsion line that keeps the luff straight and more rigid allowing it to point higher than an asymmetrical spinnaker but has a Leech Curve (as opposed to a hollow) increasing Sail Area and allowing the sail to power properly in low winds.

The torsion line is either built directly into the luff of the sail, or will use a system such as a zipper luff which allows the torsion line to be installed and removed easily.  Often furling systems such as Harken Reflex, or Profurl SPINEX, come with a specialized torsion line.

Construction

Code Zeros can be made out of either Spinnaker Nylon, a lightweight Dacron, or a Code Zero lightweight laminate (such as Contender ZL series).  As Code-Zeros are run at varying degrees and can function at a reach it is easy for sailors to push the limits of the intended speeds and angles causing damage to the sail. It’s important to know if you are going to need a sail that is more durable, lighter weight, or more performance driven – each of which has advantages and disadvantages. As a baseline, Precision Sail’s code zeros are designed with a zipper luff to allow a torsion line to be added/removed for storage and cleaning.

Heavier woven cloths, such as a 4oz Dacron, will provide durability and if you’re leaving the sail up for weeks at a time, Spinnaker Nylon is very lightweight 1.5 – 2oz, and will allow you to sail in very light winds. Finally, laminates are very performance orientated, with low stretch and very consistent sail shape; there’s also so much armamid in the Code-Zero laminate cloths that it’ll push your boat over before causing damage to the cloth, making it great for offshore sailing. A Code Zero Laminate will provide both lightweight performance in light air, and durability while crossing the pacific for an offshore catamaran cruiser with a displacement of 15,000 KG.

Catamaran Code-Zero

Many catamaran cruisers love to run a Code-Zero, just listen to Sailing Nahoa who rave about theirs!  While there are many advantages, it’s important to note that you’re going to be restricted by the rigging for how the sail is going to be able to point.  If the wide shrouds don’t allow you to sheet the sail in tight, you may not be able to hit 45° that many people expect out of the Code Zero.

Sailing Resources

Read more about Spinnakers and Code Zeros to help ensure you know what you want to know!

All About Spinnakers

Sailing With a Spinnaker – Asymmetrical Basics (Gennakers and Light Air Sails)

Sail Graphics, Colored Dacron and Color Customizations

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Cruising Code 0: For All the Angles In Between

• By Quantum Sails
• Updated: February 10, 2016

The Code 0 for cruising monohull sailboats is a full sail, shaped like an asymmetrical spinnaker, and furls easily on a top-down furling system. While the midgirth of the racing Code 0 is restricted to at least 75% of the foot length, the cruising version of the sail has no restrictions, giving the sailmaker a lot of leeway in design.

“You can make the midgirth anywhere from 55% to 75% of the foot length, allowing you to make them very deep and very flat,” says Quantum’s VP of Product Integration and sail designer Doug Stewart.

Many cruisers are intimidated by downwind sails, especially when sailing shorthanded or with inexperienced guests. The Code 0 is perfect for cruising boats because it is easily deployed on its furler and has a UV strip to protect it during a whole weekend or several days of use so that it doesn’t have to be taken down. “We find people will use this headsail more than any other on their boat,” says Stewart.

How and when to use the Code 0

The sail can be used at relatively tight angles in light air, and at very broad angles in heavier air. “It will take you through more wind angles than any other sail on the boat. Your kite is for downwind, your genoa is for upwind; the Code 0 is for all the angles in between,” Stewart says.

Rob Greven of the Netherlands-based Spirit Yachting first added a Code 0 to his sail inventory in 2009. “I was looking for a sail within my budget, easy in handling, good performance and reliable, and covering most of the wind angles.”

Now he says, he uses the sail on his Beneteau Oceanis 46 Spirit with clients and with his crew, on everything from short day trips to long-distance singlehanded racing—even the Rolex Fastnet race.

“We don’t carry a big genoa, so we use the Code 0 in light winds upwind—depending on the wind, up to around 40 degrees AWA. In the wind range of seven to eight knots, it’s possible to make seven to eight knots of boat speed. Even with our cruiser, it offers excellent performance.”

Greven says the versatility of the sail even extends to downwind running in stronger breeze between 18 to 24 knots at an angle of 160 to 170 degrees. “I’m able to sail light on the helm and with good control.”

He also carries a Quantum Vision Code 3 for downwind sailing with a full crew, but says the Code 0 is easier to use when sailing short- or singlehanded. “Since the sail is a little smaller and flatter than the V3, it’s a perfect sail for shorthanded sailing, even in stronger winds. It is better on the helm and easier to furl away,” says Greven.

Taking care of the sail

While the cruising Code 0 is designed with a protective UV cover, that cover is still very light. It will easily survive several days of use, but if you won’t be on the boat for a week or more, take the sail down, put it in its bag, and store it down below. Also, as with any sail furled on a torsional rope, if a storm blows through, there’s nothing to stop the sail from opening up. So if inclement weather is approaching, get the sail off the deck.

Greven would be the first to recommend the Code 0 to other cruisers, but says the sail sells itself.

“Last autumn, I sailed a singlehanded regatta, several days from one place to another. I almost only used the Code 0 in light winds and got a lot of positive response from other sailors.”

So while choosing a new sail for your inventory depends largely on what kind of sailing you want to optimize for, be sure to check out the Code 0. The versatility of the sail, combined with ease of use may very well prove to be the next best sail on your list.

This cruising tip has been brought to you by Quantum Sails.

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Code 0, the light and powerful sail for sailing close to the wind

While summer and high pressure are installed on your navigation basin, you dream of a few extra knots to move your sailboat. Code Zero then becomes your best friend with its few extra square meters to get you moving.

Where does this Code 0? come from?

It seems that this terminology was coined during the 1998-99 Whitbread to define a flying canopy to be used upwind. There were already Codes 1, 2, 3... for sailing from full throttle to close hauled. The term Code 0 was coined to define a sail capable of sailing at tighter angles than any other flying sail . Over the last two decades, the evolution of materials and designs has made it possible to create very specialized sails for light airs.

A large, light, free edged genoa

The Code 0 is a kind of large, very light genoa that can be sent in the manner of an asymmetrical spinnaker or as a gennaker. This sail allows to tighten the wind in very light winds. With blocked materials such as laminated fibres and a fairly flat design you will almost be able to sail upwind. On the other hand, a slightly flexible fabric and a hollow shape will not allow you to sail upwind beyond 80°.

Who is the Code 0? for?

When the calm settles in, this sail is particularly useful on racing boats without a motor. However, it is gradually gaining ground on cruising yachts , which sometimes suffer from overweight and low overlapping headsails. Code 0 with furlers is becoming a relevant solution for increasing sail area in light airs.

In regattas, can we use the 0? Code?

If you are a handicapped regatta sailor (IRC ORC...), you will be tempted to take such a sail on board. However, be careful with the measurements, otherwise your sail could be considered as a genoa , which would significantly increase the handicap of the boat . In IRC, the sail must be at least 75% of the edge at 50% of its height, in other words the shape is closer to an asymmetric spinnaker than to a genoa .

Can we turn around with a Code 0??

Tacking is not really the strong point of this sail , which will be more willing to gybe. However, if you wish to tack with Code 0, you will have to furl it in a large part before changing tack.

What are the criteria of qualité??

To be effective, the fabric should be "blocked" as much as possible with laminated materials. A nylon sail , such as a spinnaker , will only have a small range of use. In fact, when tacking to get closer to the wind, the leech will recede until it closes, which will then dump its wind into the mainsail ... all this is not very effective.

If you are using a furling system, the quality of the anti-twist luff rope is essential to roll the sail in all circumstances. The price of the rope is often directly related to its anti-twist properties. Some manufacturers such as All Purpose have developed Codes 0 that integrate the anti-torsion effect into their structure. This solution has already been validated on many racing boats and could soon win the pleasure boating market.

Can we keep the Code 0 in the mail and enroulé??

A Code 0 wrapped around its cable is a sail that will be quickly unfurled or stowed away. This equipment is not designed to stay in place full time. Although it is possible to keep it rigged for a few moments, it should be lowered as soon as the wind conditions cool down.

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Code Zero Sails Help Build a Better Offshore Inventory

• By Jeff Thorpe and Rob MacMillan
• Updated: May 8, 2012

It’s one of those perfect offshore nights: solid wind, easy swell, clear sky, and sheets eased on a headsail reach. The on-watch crew is active on the sail trim and you’re making gains on your competitor to leeward. Fast-forward three hours into the watch. The navigator sticks his head up the companionway and asks, “What happened to the boat that was next to us?”

“Well, the breeze continued to build and went aft a bit,” you respond. “They were able to continue sailing their course, but we were struggling with speed and had to head up to maintain pace with this headsail.”

“Why is he able to sail that angle but we cannot,” counters the navigator. “We’ve been working him all night.”

“We think they did a sail change, maybe a kite,” is your answer. “With the increased breeze, we can’t carry our spinnaker at that angle. It’s too risky.”

“Damn. I wish we’d brought a reaching kite instead of only runners,” the navigator sullenly mumbles.

If a similar conversation has ever occurred on your boat, you’re not alone. Building the ideal sail inventory for a particular distance race is one of the most important aspects of your race preparation. The best way to ensure you have the right sail for the right conditions is to recognize any gaps in your inventory, gaps that, once filled, allow you to sail the best angle possible at all times.

The first step is to take a good look at your existing sail inventory , and then define the designed true windspeed and true-wind angles of these sails. Divide your inventory into three parts: upwind, downwind, and reaching. You probably have one main, three or four headsails that cover you in light, medium, and heavy conditions, and likewise for your downwind sails. It’s the reaching sails that are more difficult to fit into the inventory. You’ve got jib tops, reachers, Code Zero sails, and staysails as options, and it’s here in the reaching sails where you’ll most likely have the biggest gaps.

To give some insight into building a more versatile inventory, let’s explore a few commonly asked questions.

Courtesy of Quantum Sail Design

I need to improve my reaching inventory, but I am confused by the terminology and coding of some of the sails. Most sailmakers refer to odd numbered sails (A1, A3, A5) as reaching spinnakers and even numbered sails (A2, A4, A6) as downwind-orientated sails. Code Zero sails are most effective between 80 to 125 degrees true-wind angle, in windspeeds of 5 to 18 knots. However, it’s important to remember that the Code Zero is measured as a spinnaker. You can push these sails to slightly tighter angles in light winds, but be prepared for leech flapping. An A7 is a very small sail for very big breeze, 28 knots or more. It’s typically a fractional sail. A jib top is a high-clewed headsail used for tight beam reaching.

My boat came with a typical upwind sail inventory, but my crew insists we could use a Code Zero, especially if the race turns into an upwind drifter; is this true? A common misconception is that a Code Zero can be used upwind in place of a genoa. In perfect conditions—light-wind, smooth water—a true-wind angle of 70 to 80 degrees is about as close to the wind as you’re going to get from a Code Zero. On a masthead-rigged boat with 155-percent overlapping genoas, the gap that exists between a large jib top and an A5 reaching spinnaker is not significant enough to warrant a Code Zero. On a fractional-rig boat with non-overlapping jibs, however, a Code Zero is a necessary sail because of the significant gap between the smaller non-overlapping jib and the A5 reaching spinnaker.

For a long downwind race where I may need the same sail for extended periods, how do I make sure I have redundancy in the sweet spot of my asymmetric inventory? For Transpac, and many other coastal and offshore races, the A2 spinnaker is your workhorse. But the A2 you use for inshore buoy races to sail at low angles may not be the best sail for offshore racing, when surfing waves and dealing with shorthanded sail changes. For the Reichel/Pugh 45 Criminal Mischief , we developed an A2.5, which is essentially the same size as an A2, but is much more durable. It has more reinforcement, a flatter luff, a twisted leech profile, and an oversized tack patch. This kite bridges that important gap between the A2 for flatter seas and lower angles and the smaller A4 for higher winds. This allows us to drive the boat harder in those crossover conditions, when we need to be able to put the bow up to track waves and not risk a wipeout due to the size and fullness of the inshore A2. This also allows us to sail with two A2s (A2 & A2.5) that are each efficient in a given wind range. If we break one, we still have one with which to finish the race.

I race a Beneteau 44.7 in local PHRF events. The boat has a racing main, a 145-percent genoa, a 100-percent jib, and an all-purpose spinnaker. I’m planning to do the Bermuda Race but have a limited budget. What essential sails would you recommend I add to my inventory? A 145-percent jib top, heavy genoa staysail, and reaching spinnaker would be the primary sails to focus on. There can be a fair bit of reaching in the Bermuda Race and the jib top is a potent weapon for true-wind angles between 50 to 110 degrees. The jib top offers considerably better performance in this range because the design is orientated to reaching. It also makes the boat easier to drive and more balanced, especially when paired with a genoa staysail. The genoa staysail is an extremely versatile sail that can be flown inside of headsails and spinnakers; in a seaway it can help settle the boat into balance. You should also have a spinnaker for tighter reaching angles of 100 to 145 degrees, and for better control when sailing downwind in high wind speeds. This sail will be significantly flatter than your AP spinnaker and should be made of 1.5-ounce cloth.

I’m racing my Baltic 37 in the Pacific Cup and I have three full-size symmetric kites. My boat has problems tight reaching, and we have control problems downwind in anything above 18 knots. Is there a sail that can help alleviate these problems? Because your boat is a heavier IOR-influenced design with a masthead rig and overlapping genoas, I would eliminate the symmetric spinnakers. Asymmetric spinnakers are more versatile and user-friendly offshore, especially in surfing conditions when the acceleration brings the apparent wind forward. I would first add an A3 or A5 reacher, which can also serve as a heavy-air running kite to 150 degrees, and a light-air reaching kite, which you can carry as high as 90 degrees true-wind angle. Its primary intended range is the transition zone between your jib top and your full-sized spinnakers.

An A2 or A4 runner would have the same sail area as your biggest symmetric spinnaker, but provide a better option to bridge the gap between 130 degrees and 160 degrees true-wind angle. This would also provide better control running downwind in the 16- to 24-knot range with waves. Above this range you’re back to the A5, with the reduced girths and smaller sail area to allow you to sail a bit higher true-wind angle to maintain a user-friendly groove to drive the boat around in the waves.

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Spinnaker, Gennaker or Code Zero – Which sail suits which course?

Sailing downwind we will have something completily different then sailing upwind. In the moment we entered the situation to bear away, it is like we stopped watching one movie and started with another one. This is how Tihana Tadinac, experienced regatta sailor and key account manager at Bavaria Yachts, describes when you change course after sailing high upwind and want to sail downwind. And which sail is the right sail for the downwind course? Tihana explains the differences between spinnaker, gennaker and code0.

Which sail is the right headsail for sailing with the wind?

Downwind with the spinnaker

If your boat is equipped with spinnaker equipment, you will have a perfect downwind angle. With a spinnaker you can easily sail with a wind angle of 180 degrees. So that the wind comes directly from the stern. However, directly in front of the wind, the wind speed and the speed the boat makes through the water cancel each other out. If 10 knots wind speed blows and you have a boat speed of 4 knots, the true wind is only 6 knots strong. If you change course to a wind angle of 160 degrees instead of 180 degrees, the wind vectors change. Wind speed and boat speed do not cancel each other out as much. So the boat sails faster. If the target is directly in front of the wind, it can be faster to cross in front of the wind and to jibe more often. There are different designs for spinnakers. Of course there are many different sail designs for spinnakers. Flat cuts with which you can sail higher in the wind. Full and bulbous designs for more power before the wind. Spinnaker made of light cloth for low wind, and heavy cloth for more wind. Genrell you can say that the perfect wind angle for a spinnaker is between 180 and 130 degrees wind angle.

Tips for sailing with the spinnaker

Take care of the trim

Spinnaker pole with windward sheet must always be in 90 degrees on the telltale hanging on your shroud. If you don´t have your telltale on the shroud, then put one. If you don´t put one, then you can use wind arrow on your top mast. If you don´t have even an arrow, then you should have always spinnaker pole in the extensenion of the main boom (same direction lining).  Main point of trimming the spinnaker is „to let him flow“ all the time while windward upper shoulder is slightly clapping, but not overlapping. If wind is gaining it is important to fix spinnaker with both sheets as closest to the front stay. You will be able to keep the boat steady with high waves like that.

Go fast with the gennaker

On downwind courses, you can always use gennaker too. You will need to do more gybes, but there is good chance that you will catch boats with spinnaker if you will compensate longer way caused by higher angle with higher speed. This is called Optimum Gennaker Speed. So, what we can say is main difference between Spinnaker and Gennaker:  

• Spinnaker is Simmetric. That´s why Spinnaker has 1 halyard top and 2 simmetric edges (winward sheet with spinnaker boom and leeward sheet) – no fixed point.  
• Gennaker is Asymetric and has 3 different points. The tack fixed point on the bow, or better solution fixed bowsprit. There is only 1 clew for both sheets on one place. An of course, the head as halyard point.  
• Due to this Asymmetric design, Gennaker can drive only with sharper angels and not possible to bear away like with Spinnaker. That is why Gennaker is perfect for offshore when you have winds in direction from 90 to 140 degrees.

Tips for sailing with the gennaker

But what is the main difference between gennaker and spinnaker:

The spinnaker has a symmetrical design. The spinnaker halyard at the head of the sail, the afterhaul upwind on the spinnaker pole, and the sheet downwind on the clew.

A gennaker is cut asymmetrically. The neck on the luff is firmly attached to the bow, or better yet, to the bowsprit, the two sheets to the clew, and clearly the halyard to the head. Due to its asymmetrical design, you can sail higher upwind with gennaker than with a spinnaker, although the sail area is almost the same. However, also not as low downwind as with a spinnaker. The gennaker is perfect for long space courses with a wind angle in medium winds between 90 and 140 degrees. If the wind freshens up, you can drop down to a wind angle of 165 degrees with a gennaker. By the way, with a recovery hose, setting and recovering a gennaker is very easy and safe for any cruising sailor and professional with a small crew.

Secret weapon code zero

If you are entering in the position which is slightly lower then maximum up‐wind course, light(er) conditions, too high to gain optimum speed for Gennaker, then is perfect moment for Code Zero. For Code Zero, we can say is even 1 step easier to use then Gennaker. Code Zero comes usually with the whole system with small removable furler attached to Code Zero (as fixed part of the Code Zero).  The attachment is the same as for the Gennaker. The furler is usually with removable system with elastic rope that you can attach on any place on stern that you find hard enough to holdout the force and to be clear from all other systems. It is very easy to hoist and to store. Usually it is made to hold even a bit stronger conditions. It is great sail that can compensate Genoa, but not Gennaker. With Code Zero, you are in position to achieve much more speed in lower angels then with Genoa / Jib. The maximum wind angle for a Code 0 is approximately 120 degrees wind angle.

Tips for sailing with the Code Zero

Our conclusion

So the choice of headsail on half-wind courses, space sheets or downwind courses depends on the course. Which sail you then really choose also depends a bit on the experience of the crew, the number of people on board and the area of use. For cruising sailing, the gennaker and code 0 are certainly easier to handle. If you are a sailor who is a bit more confident and have at least three people on board, you will have a lot of fun sailing a spinnaker. Any sailmaker will certainly be happy to advise you.

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Code zero sails to cover a wide range of AWA

A quick history of code zero sails

Code zero (also written code 0) sails originate in a rating rule workaround where a clever designer was trying to design a tight reaching sail that could be rated as a spinnaker. This development opened up all sorts of thinking around flatter spinnakers and resulted in numerous new types of sails and denominations driven in part by actual sailor needs… and in part by imaginative marketing.

Code sails cover a very wide range of AWA, from “almost-a-closed-haul-genoa” to “almost-a-running-asymmetric” sail.  In this note we will try to clarify the needs of cruisers and casual racers when it comes to Code Zero sails, the 3 Code Zero sails developed by iSpinnakers, and explain what sail types, cloth, and furling options are available to meet those needs.

Who can benefit from a Code Zero / Code Hybrid / Hybrid sail?

Apart from high end, money-is-no-object race programs, there are 3 broad situations where a Code Zero sail is highly beneficial:

1. Boats with non overlapping / self tacking jib  – Code 0 target apparent wind angles AWA 40-100

On a boat with a non overlapping headsail, there is a significant power loss as soon as you bear away from closed haul. A flat, fairly narrow, furler-mounted Code Zero / code 0 can take you from almost closed haul to a hair below beam reach, where the downwind sail(s) will take over.  Racers that must count this sail as a spinnaker will be constrained to a minimum width (75 % of foot), while sails designed for cruisers do not have that constraint and will be narrower.  Look at our Code 0 TR concept for this kind of sail in our range.

2. When looking for a true reacher (often called screecher) Code Zero – Code 0    target apparent wind angles  AWA 60-120 

This is the workhorse code zero for most situations:  

• you have a spinnaker or deep gennaker for deep downwind / running, and
• your genoa is not very big, leaving you with a power gap in broad to tight reaching angles. 

This sail that will take over reaching duty from broad to tight reaching and bridge the gap between genoa/jib and full downwind sails.  It is wider, and with a medium draft.  In our range look for the Code Zero MR concept.

3. When looking for a broad reaching sail Code 0 target apparent wind angles AWA 80-130

• The boat may have a symmetrical for running and is looking for a broad reaching sail, to bridge the gap with the genoa –  OR
• you might have a very fast boat (catamaran or trimaran). With great boat speed, this code zero that can get as low as 130 degrees Apparent Wind Angle will be carried into true wind angles where slower boats would need to sail their asymmetric.

This is an even wider and deeper sail, at times getting closer to spinnakers. A top down furler may be used for this sail.

In our range, look for the code Zero BR concept.

iSpinnakers range for Code Zeros

As seen above, there is an infinite number s  of variations in code zero sails to cover a very wide range of AWA, playing on girth and draft, cloth style and furling system.  To simplify choosing the right sail we have developed 3 concepts that cover the entire range, with further customization of each concept available for your boat and program .

Code Zero TR by iSpinnakers AWA (Apparent Wind Angle) range 40 – 100 *.

This primarily upwind sail is flatter and narrower than its sisters below, with a mid height girth of about 60%, +or- 5% for cruisers. Racers may be constrained by their rating system to minimum girth of 75% .

This sail has a nearly straight luff and is generally designed with a built-in antitorque rope, and to be used with our Seldén CX furlers. 

It does require a lot of tension in the luff, and 2:1 purchase is recommended either at the halyard or at the tack line.

The iSpinnakers Code Zero MR – AWA (Apparent Wind Angle) range 60 – 120 ( à 140 *. )

Our most popular concept, to complement your symmetrical spinnaker, or A2 style asymmetrical spinnaker. Perfect for a boat that has an overlapping genoa that will be used for tighter reaching angles. Mid height girth of 70% +or- 5%, medium draft for reaching power. 

You can use either a top down (Seldén GX) or a bottom up furler (Seldén CX). If you also have (or plan to get) a complementary A2 asymmetric / gennaker, ask us about the Seldén conversion CX/GX kit that lets you invest in a single furler unit that can be used with both sails. The CX mode will be used with the code Zero while the GX mode will be used with the A2 asymmetrical spinnaker.

The iSpinnakers Code Zero BR – AWA (Apparent Wind Angle) range 80 – 130   (à 150*. )     

This sail is even wider with a mid girth of 80% +or- 5%, and draftier. It can get close to an A3 or A5 spinnaker and a top down furler (Seldén GX) is best .

* These apparent wind angles are optimum and provide maximum sail performance – the sails can of course be carried below those wind angles, and will keep powering the boat strongly. However outside of the optimal target range, the sail will not have the best possible performance (just like a 150% genoa can be carried effectively to 150 degrees or beyond– but will not pull as hard an A2 Asymmetric)

Cloth choice, furling, storage, etc .

Cloth choice.

For all these sails, there are 3 main choices:

• The go-to solution is a Code Zero specific film with reinforcing fibers (polyester, aramid, etc . ).  We use primarily the CZ range from Dimension-Polyant, a film with reinforcing fibers in Polyester or Aramid. One side is reinforced by a rugged white or grey taffetas. There are also race oriented versions of the CZ cloth, with more exotic fibers, and no protective taffetas. 
• For the MR and BR versions, a more economic but heavier solution is to use a heavy spinnaker cloth, such as Challenge NFS 94 (2.2 Oz) and NFS 144 (3.4 Oz). This is a great option for sails up to 50 sqm, beyond which weight becomes prohibitive. As an added benefit, the cloth is available in dark blue, red, black, and white, and not just grey and white.
• For high end racing applications, we can also build the sail in a string membrane.

Furling and sock

The deepest drafted versions of our Code Zero BR concept require a top down furler (Seldén GX). All other versions can be used with a top down (Seldén GX) or bottom-up (Seldén CX) furler. 

For a more economical solution, the MR and BR versions can also be used with a sock when built in spinnaker cloth. The sock is a proven and economic solution for retrieving these sails. It requires, however, a crew member on the foredeck for launching and retrieving the sail.

Anti Torque system

Top down furlers (GX) have their own antitorque rope as part of the furler.

Bottom up furlers (CX) have the anti torque system built into the sail, and we offer 2 options:

• The “classic” anti torque rope built into the sail luff (we use Vectran ropes)
• A cable-less version, where a series of carbon tapes glued strategically in a lens shape along the luff provide the anti torque function. (For sails built in spinnaker cloth, we add a luff area (10% of total sail area) made in Code Zero cloth to allow the application of the carbon tape cable-less system.)

The cable-less version is lighter and a joy to handle….It also requires less luff tension than a sail with a built in cable, and thus does not require a 2:1 purchase on the halyard or tack line.

A side note on the topic of furlers – An A2 Asymmetrical spinnaker (either custom or chose from our standard cut range) and Code Zero BR or MR are a great combination –  we can provide you with a single furling system that will handle both sails using the Seldén CX/GX converter – As already mentioned above, this is a great solution that prevents you from having to purchase 2 separate furlers.

Code Zero sails cannot have a UV Band (unlike Genoa) and must be stored quickly when not in use, to avoid UV damage. A number of bag solutions are available, but we recommend a 2 meter Genoa-style long zipper bag, in which a furled sail can be flaked neatly. For sails used with a sock, a box bag or just a regular cinch bag are great.

CX luff tension

For the sails with a built-in AT rope, regular tension on the halyard is NOT enough. You need to install a 2:1 purchase system.

• At the Halyard you can use a dead end fitting and a special block:

• At the tack you can use a special low friction shackle at the bottom of the furler, which also makes it easier to connect the furler from the fore deck if you have a bowsprit:

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Code Zero TWA

• Thread starter JRT
• Start date Nov 19, 2019
• Forums for All Owners

While I really want a full set of new sails, the reality is I have a lot of improvements to work on. I do think after our first season with the 310 I really need a lite air sail. The recommendations so far are code zero or cruising spin. The code zero says can be used up to 45 deg TWA, cruise spins is up to 90 deg. I don't spend much time running downwind but do seem to need to go upwind on very low wind days more. So question, is 45 deg TWA realistic? Is Code zero a good first spin type sail? I had a drifter on my O'Day 25 that was hank on and was just wonderful to fly on the low wind days we get here and I miss that capability now with the 310.  

A code 0 is extremely versatile and great is light winds. It can be flown from 40 to 140 AW. Aysemetric spin best 90 to 180 AW. But you’ll need a bowsprit to fly either properly. I recommend Selden retractable.  

JRT said: While I really want a full set of new sails, the reality is I have a lot of improvements to work on. I do think after our first season with the 310 I really need a lite air sail. The recommendations so far are code zero or cruising spin. The code zero says can be used up to 45 deg TWA, cruise spins is up to 90 deg. I don't spend much time running downwind but do seem to need to go upwind on very low wind days more. So question, is 45 deg TWA realistic? Is Code zero a good first spin type sail? I had a drifter on my O'Day 25 that was hank on and was just wonderful to fly on the low wind days we get here and I miss that capability now with the 310. Click to expand

Thank you soo much @DrJudyB ! I was really looking for that feedback to understand my expectations.  

AlastairLC said: A code 0 is extremely versatile and great is light winds. It can be flown from 40 to 140 AW. Aysemetric spin best 90 to 180 AW. But you’ll need a bowsprit to fly either properly. I recommend Selden retractable. Click to expand

Pizzazz said: I do not fully understand the rationale for a code 0.... If a code 0 is flown between 40 and 140 AWA, what is the benefit compared to a 155% genoa that can be flown between 30 and 130 AWA Click to expand

Pizzazz said: . If a code 0 is flown between 40 and 140 AWA, what is the benefit compared to a 155% genoa? SV Pizzazz Click to expand

Pizzazz said: I do not fully understand the rationale for a code 0 given the above but I have little experience with downwind sails. If a code 0 is flown between 40 and 140 AWA, what is the benefit compared to a 155% genoa that can be flown between 30 and 130 AWA, works with greater wind ranges (10-25 knots) and can be easily reefed in bad weather? Is the material lighter, so that it is more efficient in light winds (5-10 knots)? I agree that an asymmetric can be flown from 90 AWA to close to dead downwind but typically, it is a different cloth for different wind speeds. You need a large asymmetric to give you decent speeds at say, 10-12 knots true wind speed/170 AWA. The same sail will overwhelm most boats/captains at 15 knots/90 AWA. May be I am exaggerating a bit but it seems to me that downwind sails have very specific wind speed/AWA sweetspots. SV Pizzazz Click to expand

Thank you, it is very helpful to understand the evolution of the sail plans and the reasons all these sails were developed. I am not trying to steal the thread but it could be helpful to all of us if someone could give a historical perspective on sail plans. The way I understand it is: Boats from the eighties had a mast head rig, multiple jibs/genoa's and relatively small mains. They would typically use spinnakers for downwind sailing. The 155% genoa was/is a versatile sail for those rigs. Then people realized one sail weight is not enough for all wind speeds/angles, so they moved the rig forward, making it a fractional rig with smaller jibs. The jib became an upwind sail only and most of the drive was coming from the main. Spinnakers went out of favor because they are too much work. Instead of having one heavy genoa, now you have a small jib for upwind work and an asymmetric for broad reaching. Then people realized that if you have a flatter stern and sufficient power you develop more speed and better VMG downwind when broad reaching, so now you have a number of asymmetric/code 0 whatever sails that maximize the broad reaching speed. Is this approximately correct? The question then is, if I have an eighties boat (Hunter 31) and my downwind performance is lacking, what is best for me? Get a spinnaker and learn how to manage it single handed or get an asymmetric and gybe downwind? Not only in terms of speed but also in terms of handling, cost to install (i.e. polling out the genoa is easy, while having a spinnaker pole is a lot of cost and effort, rigging, etc.). An asymmetric would be an easy addition (just a hallyard, possibly a sprit) but will it give me good VMG downwind given that my stern was probably not designed for an asymmetric? Ideally, I would like to compare polars of similar boats to my Hunter 31 for polled out 155% genoa, asymmetric and symmetric? Thank you, SV Pizzazz  

Pizzazz said: Thank you, it is very helpful to understand the evolution of the sail plans and the reasons all these sails were developed. I am not trying to steal the thread but it could be helpful to all of us if someone could give a historical perspective on sail plans. The way I understand it is: Boats from the eighties had a mast head rig, multiple jibs/genoa's and relatively small mains. They would typically use spinnakers for downwind sailing. The 155% genoa was/is a versatile sail for those rigs. Then people realized one sail weight is not enough for all wind speeds/angles, so they moved the rig forward, making it a fractional rig with smaller jibs. The jib became an upwind sail only and most of the drive was coming from the main. Spinnakers went out of favor because they are too much work. Instead of having one heavy genoa, now you have a small jib for upwind work and an asymmetric for broad reaching. Then people realized that if you have a flatter stern and sufficient power you develop more speed and better VMG downwind when broad reaching, so now you have a number of asymmetric/code 0 whatever sails that maximize the broad reaching speed. Is this approximately correct? The question then is, if I have an eighties boat (Hunter 31) and my downwind performance is lacking, what is best for me? Get a spinnaker and learn how to manage it single handed or get an asymmetric and gybe downwind? Not only in terms of speed but also in terms of handling, cost to install (i.e. polling out the genoa is easy, while having a spinnaker pole is a lot of cost and effort, rigging, etc.). An asymmetric would be an easy addition (just a hallyard, possibly a sprit) but will it give me good VMG downwind given that my stern was probably not designed for an asymmetric? Ideally, I would like to compare polars of similar boats to my Hunter 31 for polled out 155% genoa, asymmetric and symmetric? Thank you, SV Pizzazz Click to expand

Pizzazz said: The question then is, if I have an eighties boat (Hunter 31) and my downwind performance is lacking, what is best for me? Get a spinnaker and learn how to manage it single handed or get an asymmetric and gybe downwind? Not only in terms of speed but also in terms of handling, cost to install (i.e. polling out the genoa is easy, while having a spinnaker pole is a lot of cost and effort, rigging, etc.). An asymmetric would be an easy addition (just a hallyard, possibly a sprit) but will it give me good VMG downwind given that my stern was probably not designed for an asymmetric? Ideally, I would like to compare polars of similar boats to my Hunter 31 for polled out 155% genoa, asymmetric and symmetric? Thank you, SV Pizzazz Click to expand

Thank you, it all makes more sense now. I am quite happy with just polling my genoa in light winds and above 15 knots I make close to hull speed anyway. The only problem is that I lose poles approximately once a year but that is just being clumsy. So, for a trip Marina del Rey to Hawaii, cruising, should I get an asymmetric or just a spare pole? I estimate it would make a difference of 1-2 days max. in terms of the total journey time.  

Jackdaw said: The current joke is 'race boats used to carry 4 headsails. Now they carry 1, but 4 spinnakers'. And that's true for us! Click to expand

This is great info and help! I'm 99% of the time looking to just move around the lake on our limited days we can and it seems low wind days are not great with the 135 jib and main. I also noted in our river race a few weeks ago the only boats I think that managed to finish a lap in the time limit had spins / code 0 / drifters. Cost wise this seems like a no brainer to me, a code 0 on my boat in 1.5 oz single color is under $1700 from Precision with their black Friday discount. I know it doesn't fix all points of sail but should help fill in some with the wind conditions we have. The Hunter 31 is pretty similar to the Cataline 310 looking at sailboat Data info so I would guess a similar price.  

Pizzazz said: I think that is the core trade-off for cruisers. I carry a 155% and a 110% genoa's for my boat, so I have only one sail to store. It is not that much work changing the sails over, although taking the 155% off the furler in a breeze is messy on the deck. Still, it is only one extra sail to store. Now, if I get 1-2 spinnakers + the lines and the spare main and there will be no space on the boat for myself. Ideally, I should get an asymmetric on a second furler on a bowsprit as you suggest but this is something like a $4-5,000 expense comparable to a new engine . Click to expand

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Computer Science > Computational Complexity

Title: perfect zero-knowledge pcps for #p.

Abstract: We construct perfect zero-knowledge probabilistically checkable proofs (PZK-PCPs) for every language in #P. This is the first construction of a PZK-PCP for any language outside BPP. Furthermore, unlike previous constructions of (statistical) zero-knowledge PCPs, our construction simultaneously achieves non-adaptivity and zero knowledge against arbitrary (adaptive) polynomial-time malicious verifiers. Our construction consists of a novel masked sumcheck PCP, which uses the combinatorial nullstellensatz to obtain antisymmetric structure within the hypercube and randomness outside of it. To prove zero knowledge, we introduce the notion of locally simulatable encodings: randomised encodings in which every local view of the encoding can be efficiently sampled given a local view of the message. We show that the code arising from the sumcheck protocol (the Reed-Muller code augmented with subcube sums) admits a locally simulatable encoding. This reduces the algebraic problem of simulating our masked sumcheck to a combinatorial property of antisymmetric functions.

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